From publisher blurb:
The Dungeons in Blue series brings classic blue maps to the virtual tabletop! These ready-to-fill maps are packed with rooms, corridors, pits, and caves; all judiciously sprinkled with tricks and traps. Every geomorph tile seamlessly connects to every other tile in the series, providing the megadungeon builder tremendous freedom and flexibility.
All maps are ready-to-use PNG-format files compatible with most virtual tabletops. Use them as-is, or combine them into larger maps using your favorite image processing software.
Our map philosophy is simple: show the permanent features of the area without unnecessary clutter. Our maps aren't marked up with creatures or minor furnishings, leaving plenty of space for the GM's additions.